Google adds validation to DNSSEC

Worldwide, the rollout of DNSSEC can comfortably be described as “glacial”, but Google valiantly continues to try to give it profile. Having launched its own DNSSEC service three years ago, Mountain View has now added DNSSEC validation to its public DNS resolvers.

Announced in this blog post, Google says the move means “we can better protect people from DNS-based attacks and make DNS more secure overall by identifying and rejecting invalid responses from DNSSEC-protected domains.”

Until now, Google notes, it accepted and forwarded DNSSEC-formatted messages without validating them. This meant that while its own DNSSEC responses were trustworthy, those it forwarded may not have been.

As noted by DSL Reports in January of this year, DNSSEC implementations remain rare.

Google agrees, stating that currently only seven per cent of the 130 billion DNS requests it resolves on an average day are DNSSEC-enabled, and only one per cent of server responses are signed. That means most of the Internet remains vulnerable to the so-called “Kaminsky bug” – fake DNS records that redirect users to malicious Web sites, injected by DNS cache poisoning.

What's it all about?

As readers will know, DNS – the Internet's lookup system that matches a readable URL (theregister.co.uk) to an IP address (92.52.96.89) – was originally based on trust, and it assumed that trust long after bad actors learned how to exploit the DNS to direct users to malicous sites.

To get some context for the announcement, The Register spoke to APNIC chief scientist Geoff Huston, who says it's a good move, partly because his research suggests Google is gaining importance as a DNS resolver.

In research that identified 2.5 million DNS clients, Huston said Google DNS was in use by as many as 15 percent of them, making it a big enough resolver to influence the rest of the industry.

Prior to this announcement, he explained, an address might resolve even though Google had not tested the DNS signature key against the site's certificate. With validation in place, Google is committing itself to signature-checking all responses. If there's a mismatch – which Huston noted could just as easily be because of an error rather than malice – Google will return a SERVFAIL (the impact of which is that the end user will get a "site not found" error).

“I've seen some very big sites that only worked by accidental glue”, he remarked. “Anyone doing proper DNSSEC on them will get a SERVFAIL from Google.

“You can't do DNS at 4.59 on a Friday afternoon! You have to follow the instructions to the letter, no shortcuts, no crap – because otherwise you will have a badly signed domain and a large amount of the internet won't see you any more. DNSSEC validation means anything wrong with a domain certificate, or the parent, all the way back to the root, makes a SERVFAIL.”

That, he said, will ultimately be a good thing because it will encourage sites to lift their game.

Huston believes any site that's entrusted with customer data should already be using DNSSEC. “I would expect all banks, all government sites, to use signed domains … if you haven't locked the DNS, it's close to negligence”.

There is, however, a hole in the local industry which may well be common worldwide. It's still very uncommon for companies selling domain name services to offer usable tools for site owners to create their own site signatures. That needs to change to become a basic part of the service, “because the beneficiary of DNSSEC signing is everybody”. ®